I always thought it was his brains leaching out. ;-)
Something weird. Years ago I was watching the news and they cut to a meeting with Ronald and Gorby. When they first went to the meeting the blotch was on one side of his head and the news suddenly dropped the live feed. When they came back I swear the damn blotch was on the other side of Gorbachev’s head. I kid you not. I always wondered if anyone else caught that.